There already exist a large number of closure systems for containers, including closure systems for plastic containers. The majority of these systems, however, do not guarantee the necessary tightness or degree of seal which is required for the long-term preservation of food products and the like. These systems include those which employ various types of fittings between the edge of the container wall and a groove located at the periphery of the lid. None of these previous systems thus provide the necessary tightness required by certain packaged food goods, especially that which could be sufficient to provide for the long-term preservation of food products therein.
Up till to present time it has therefore remained the case, particularly with canned food products such as canned fish, sausages, soups, jams and the like, that they have to be packed almost exclusively in metallic or glass containers employing mechanical enclosure systems. Most of these systems thus include sealing rings in order to provide the necessary air tightness to preserve these products for long periods of time, including periods of up to from two to five years. However, when employing these types of metalic or glass containers, even though they might have the necessary characteristics for such applications, these systems are clearly not a favorable solution from an economic point of view, particularly since there are other materials, such as various plastics, which are available and which are much cheaper and easier and less costly to process than are metal and glass containers. For that reason, plastic containers have recently been replacing the previous metal and/or glass containers, but it has been necessary to maintain the overall use of a metal lid in order to guarantee the tight fitting nature and seal provided by these containers along with easy opening thereof. Additional attempts have also been made to apply the same prior mechanical sealing arrangements which have been used with metallic parts to plastic components, but these have not been successful. For example, the use of friction or ultrasonic welding has been attempted, but this has been found to be impractical because it does not allow easy opening of the container, and because of the restrictions imposed by certain goods which are to be packed in these containers. For example, in the case of canned fish, it is necessary for the container to be completely filled with liquid fat or the like, and thus at the time of placement of the lid on the container overflow occurs, which prevents proper welding of the plastic surfaces thereof. A particular example of such a prior system is shown in Switzgable Jr., U.S. Pat. No. 3,204,801, which shows the use of a metal band 20 in connection with a resilient stopper 10 made of plastic, and employed in connection with a bottle or metal container 14 which is preferred by this patentee, even though mention is made of plastic cans for use therewith. In any event, the metal band 20 in this patent extends across the overall surface of the stopper 10, and has a notched lower edge 28 crimped to engage the container neck below bead 18 thereon. This closure thus relies upon radial stress created across the overall surface of the container acting against the rigid surface of the bottle or metal container 14 to create a seal. Summers, U.S. Pat. No. 4,111,331 discloses another closure which in this case includes a plastic container with an externally threaded outlet 21 extending outwardly from a circumscribing annular male boss 46. In this case, the outlet is closed with internally threaded plastic cap 24 having a flared annular skirt portion 28, and upon threaded engagement, the skirt portion is sealed to the male boss by means of a crimped metal ring 25. Additional such closures are shown in patents such as U.S. Pat. Nos. 937,847, Norton; 1,838,323, Nielsen; 2,406,568, Sebell; 2,619,246, Staller; 2,961,111, Nesme; and other such patents.
All of the above have thus constituted unsuccessful attempts to produce commercial products by which manufacturers of various products, in particular foodstuffs, have been unable to employ plastic in both components, namely the base and the lid of a container, to package such goods for preservation over long periods of time, such as two years or greater. In addition, the potential ability to use such plastic containers not only results in considerable savings, but also permits the use of different technological processes in the manufacture of these goods, such as in connection with canned fish production, where conventional methods for cooking and sterilization are still in use inspite of being time and energy consuming. On the other hand, with these plastic containers it becomes possible to use faster and more economical cooking and sterilization processes, such as microwave ovens, for example. The ability to do so could further substantially reduce production costs if possible. It is therefore an object of the present invention to overcome these prior difficulties and produce such a sealed container system.